Scuds are large shrimp-like amphipods that are amongst the common crustaceans collectively known as "beach fleas." They are also known as "sideswimmers" for their distinct swimming style. Gammarids tend to be found closer to the water's edge than the more terrestrial orchestrids. Species identification is difficult in scuds. Typically less than an inch long in our area, some Arctic species can reach two inches.

Barnes, R.D., Invertebrate Zoology, 1980, Saunders College and Holt, Rinehart and Winston.